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July 6, 2003

Hack the ScreenSaver, Zap the PMU

Apparently, the password-protection of the MacOSX screensaver is vulnerable to a buffer overflow. Presumably, this is a flaw in the Cocoa Frameworks, because no one programming the password-entry field of a security module would be dumb enough to allow an extra-long password to crash the module.

Anyway, I hope Apple fixes this soon. (Update:Security Update 2003-07-14 has the fix.)

In other news, my practically brand-new (a month old) iBook battery started acting wonky. When plugged-in, the “time to recharge” would always say “Calculating …”. When on batteries, it would give reasonable “time remaining” readings, but the percentage readings would be totally off (e. g. “2%” remaining, when I purportedly had “2:58” of time left).

So I followed Apple’s advice to recalibrate the battery — let it drain down fully till the machine goes to sleep, then plug it into the AC and let it recharge fully. Big mistake! The battery drained down to 0%, but then it would not recharge. I tried following the instructions to reset the PMU, to no avail.

I was getting a bit frantic. These batteries are expensive suckers, and I’d just bought this one.

In desperation, I turned to the Apple Discussion Boards. These are typically useless, containing endlessly repetitive post whining about this or that problem (there are lots of iBook battery posts), or Apple Support’s response to same, with nary a piece of useful advice to be found. [There are, it should be said, no Apple employees contributing to the Discussion Boards. Apple’s only role, aside from hosting the site, is to delete the occasional post for violating a set of extremely arcane rules about what is permissible.]

Anyway, after reading through several hundred mind-numbing posts, I finally found one which offered a glimmer of hope. One guy with a similar problem had found that the solution was to reset the PMU, not of the iBook, but the one onboard the battery. The technique, apparently, is to briefly short-out the two outermost terminals of the battery. This did not sound like a great idea — I was a kid the last time I deliberately stuck a wire between the two terminal of a battery to watch the sparks fly — but since I had nothing to lose and about $180 to gain, I did as he suggested, reinserted the battery and lo and behold! it began to charge.

Posted by distler at July 6, 2003 1:00 AM

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Re: Hack the ScreenSaver, Zap the PMU

I have run into the same problem as you– my iBook battery just won’t charge up. Is there some special way of shorting the iBook battery? Do I have to connect the terminals for a certain amount of time?

Re: Hack the ScreenSaver, Zap the PMU

After charging the battery for about 10 minutes (adding about 1-3 percentage points of additional charge), the laptop’s power-ring turns from orange to green and it won’t charge any more – unless I remove the battery and reinsert it. Then, the process begins again, and I get another few percentage points of power, but that’s all.

I have tried what I believe to be all the OTHER standard remedies in various combinations: Power Manager Reset, zapping PRAM (Command-Option-P-R as well as Tech Tool), System 9 and OS X (the rebuild of 10.2.8), booting from the laptop’s hard disk and booting from CD, the Open Firmware commands “RESET-NVRAM” and “RESET-ALL,” Battery Amnesia software (under System 9) ….

And yet the problem persists: Just a few percentage points of additional juice per recharge-after-battery-removal-and-reinsertion.

Seems as if the battery itself is fine; it’s less than a year old, and – once I get it recharged using this clunky method – it runs the computer just fine, for a long period of time.

So: Is it time to zap the battery, as described on this page?

Do the symptoms I’ve described match those of others who have proceeded to use the battery-shorting method?

Has anyone ruined a battery in this fashion?

And is there an optimal charge level for the battery to hold at the time the terminals are zapped?

Re: Hack the ScreenSaver, Zap the PMU

Re: Hack the ScreenSaver, Zap the PMU

John-
I have an original blueberry with the same problem. did the shorting-out trick work for you? exactly which terminals did you short?

From Xcharge i know my batt has 10.12V (while charge indicator is green); then charging starts (amber) and voltage jumps to 16.6v. i guess my best bet is to put a volt meter on the battery to try to find the 10.12v and try shorting that..

Re: Hack the ScreenSaver, Zap the PMU

Another successful use of this technique! My wife’s iBook was not charging, in fact it would decide there was no battery installed after about two minutes of charging while the battery status said “calculating”.
This battery had one LED on it that was constantly on. Not when you pressed the button, but all of the time. This made me think it was definitely in the battery, not the computer. Also, the fan on the computer was on constantly even though the air running through it was cold. I don’t know if it was related because the fan stopped when I restarted the computer. But the battery was not fixed.
So, I followed the instructions. I placed a razor blade in each of the two outermost terminals and shorted them by touching both with a screwdriver for an instant only. I got a spark and I immediately turned the battery over to see if the LED was out. The LEDs blinked a few times, then it went through a sequence of one, then two, then three then all four lit. It did that sequence a few times and then the all went out.
When I pushed the button on the battery, three LEDs lit up for a few seconds and then the all went out. Perfectly normal behaviour!
I put it in the iBook and it now is charging and shows 1:18 to full charge!

It took only a split second and I assume that interrupted the power to the internal processor which caused the reset.